The invention resides in a camshaft adjuster for an internal combustion engine including a control valve with a valve housing in which a control spool is disposed for controlling the supply of hydraulic fluid to an actuating unit for adjusting the angular position of the camshaft relative to the crankshaft of the engine, the control spool being operable by an electric motor and a transmission structure.
For reducing the fuel consumption and raw emissions and increasing the power output and torque, internal combustion engines generally include control devices for adjusting the angular position of the camshaft relative to the crankshaft. At this time, mostly hydraulic vane cell adjusters including hydraulic actuating chambers are used. The angular adjustment of the camshaft is achieved by the controlled admission of hydraulic oil from the engine lubricating circuit to the chambers of the hydraulic vane cell adjuster by means of a control valve. The control valve is operated by an electromagnetic device.
DE 36 19 956 discloses a camshaft adjuster of an internal combustion engine with a control valve which is disposed in the camshaft and which includes a control piston disposed in a valve housing. The camshaft is provided with an operating unit for adjusting the angular position of the camshaft relative to the crankshaft of the engine under the control of the control valve. The control piston is actuated by an operating unit which includes an electric motor; and a motion transmission structure which moves the control piston in an advancing or retarding direction. As operating unit, an electric motor with an operating rod, which is capable of axially moving the control piston, is used. The use of the operating rod however requires an expensive control arrangement for the positioning of the operating rod since the motor must be energized for the back and forward movement of the operating rod.
It is therefore the object of the present invention to provide a camshaft adjustor for an internal combustion engine having a simple, reliable and relatively inexpensive control arrangement for the adjustment of the angular position of the camshaft relative to the crankshaft of the engine.